The body system responsible for hormone regulation is the endocrine system. This system consists of various glands, such as the pituitary, thyroid, adrenal, and pancreas, which produce and release hormones directly into the bloodstream. These hormones act as chemical messengers that influence virtually all aspects of bodily functions, including metabolism, growth, mood, and reproductive processes. The endocrine system works in tandem with the nervous system to ensure homeostasis, responding to internal and external stimuli by modulating hormone levels and maintaining balance within the body.